Once your screen has been degreased and dried you will be ready to coat it with emulsion. There are two types of emulsion, liquid emulsion and capillary film.
Direct Liquid Emulsion
Liquid emulsion is spread onto the screen mesh with a tool called a scoop coater. Scoop coaters come in a variety of sizes and have two coating edges, one for thick coats and one for thin. The decision to use one edge or the other will be based upon the thickness of the stencil you will need for your print.
- Photopolymer emulsions are emulsions that are premixed with sensitizer by the manufacturer so that they are ready to use straight out of the container.
- Most photopolymer emulsions will have a faster exposure time than will dual cure emulsions. Because these emulsions can go from under-exposed to over-exposed in a matter of seconds, they are most often less forgiving of errors during the exposure process.
- Because exposure times must be accurate to within a few seconds, photopolymer emulsion is recommended for use in shops that have a very controlled prepress and exposure process.
- Dual cure emulsion is a two-part product that arrives to the user in two separate containers. The user will mix the sensitizing agent with water and then stir the mix into the emulsion base.
- Dual cure emulsion is most often slower to expose than is photopolymer emulsion.
- Because dual cure emulsion allows for a variance of as much as 30 seconds in exposure time, it is a popular choice of beginners and shops with varying prepress and exposure processes.
Capillary film on the other hand, is applied to the screen mesh by placing the film onto the moistened screen mesh and using a squeegee to smooth it against the surface of the mesh. As with liquid emulsion you will want to let the screen and emulsion dry before use.
- Capillary film is an easy to use and inexpensive means of emulsifying screens. Capillary film is offered in sheets of varying size and thickness. Because capillary film allows a printer to take a screen out of the box and have it ready to print in a matter of minutes, it is quickly becoming the preferred method of busy shops.
- Capillary film allows printers to know with certainty that they are achieving optimum stencil thickness.